Add geotiff edge-case tests: IFD loops, header parsing, descending-y, non-georeferenced (#1482)#1492
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…1495) test_merge_dask_different_crs_matches_eager intermittently SIGABRTs on macOS CI runners. The merge() dask graph creates a fresh pyproj.Transformer per chunk, and PROJ's first-time CRS-database load is not safe under concurrent threaded workers — multiple threads racing to init the SQLite DB on macOS triggers an abort. The test exercises dask graph correctness, not dask threading. Pin it to the synchronous scheduler and pre-warm pyproj.CRS objects so the parity assertion runs without the threading dimension. CRS thread-safety in the production reproject path is its own concern and is not regressed here. Refs the same crash on PR #1492 macOS-3.13 and on main run e253900 (macOS-3.12).
Tests: - IFD chain loop / cycle detection in parse_all_ifds - RATIONAL/SRATIONAL with denominator=0 returning 0.0 - RATIONAL with count overflowing the buffer - Truncated IFD entry buffer - BigTIFF malformations (offset_size != 8, truncated header) - Classic TIFF first-IFD offset past buffer - Descending-y (south-up) write/read round-trip - Non-georeferenced TIFF read produces integer pixel coords Code: - _extract_transform now returns (transform, has_georef) so callers can tell "no GeoTIFF tags" apart from "tags present with default values". GeoInfo carries the new has_georef flag. - _geo_to_coords falls back to integer pixel coords (0..N-1) when has_georef is False, instead of producing y values like -0.5, -1.5, ... from the default unit transform.
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Closes #1482.
Summary
21 new tests in the geotiff module, plus one small reader fix.
Tests cover:
parse_all_ifdsalready had aseenset; this adds a test that builds a malicious buffer where IFD2 points back at IFD1, so the guard can't regress silently._read_valueedge cases: RATIONAL/SRATIONAL with denominator zero, RATIONAL count overflow, truncated IFD entry buffer.offset_size != 8, truncated 8-byte BigTIFF header.crsattr, instead of fractional coords from the default unit transform.Code change
_extract_transformnow returns(transform, has_georef).GeoInfocarries a newhas_georefflag._geo_to_coordsfalls back to integer pixel coords whenhas_georefis False. Existing georeferenced reads behave identically.Test plan
pytest xrspatial/geotiff/tests/test_header.py xrspatial/geotiff/tests/test_georef_edges.pytest_features.py::TestPaletteare unrelated and present onmain.